Improved method for pressure baking of carbon articles



2,965,931 Patented Dec. 27, 1960 IMPROVED METHOD FOR PRESSURE BAKING OF CARBON ARTICLES Lorne B. Alden and Frank P. Holloway, Fostoria, Ohio, assignors to Union Carbide Corporation, a corporation of New York No Drawing. Filed Oct. 24, 1957, 'Ser. No. 692,034

2 Claims. (Cl. 123-475) This invention relates to the use of a sulfur-containing mix in the production of shaped carbon articles by pressure baking.

A recently developed pressure baking method for producing carbon articles comprises confining in a refractory lined mold, a mixture of finely divided carbonaceous particles with a fusible and carbonizable carbonaceous binder susceptible of thermal decomposition subjecting the mixture within the mold to a high mechanical pressure of the order of 4500 pounds per square inch to compress the same, and passing an electrical current of about 500 amperes per square inch of compressed mixture in the mold to heat the mixture to a temperature at which substantially complete carbonizing of the binder constituent occurs. By means of this process, it is possible to pro duce in about eight minutes carbon articles which heretofore required a production time of eight weeks.

In the above-described process, pitch and certain other binder materials produce volatile substances which condense on the press, punches, and cold sections of the mold. Accumulation of such substances prevents or interferes with proper operation of the equipment, and in extreme case can occasion minor explosions.

The main object of the present invention, therefore, is to provide means for preventing the accumulation of condensed volatile material on carbon-baking equipment employed in the process described.

This object is achieved in accordance with the present invention, which is based upon the unpredictable discovery that the addition of finely divided sulfur to the binder material or green unbaked mix results in reactions which, at the process temperature, slightly increase the deposition of binder carbon and more characteristically, produce largely non-condensing volatile gases, thereby avoiding the accumulation of unwanted material on the equipment.

In the practice of the inventiomsulfur is added in a quantity ranging from 3 to 20 percent by weight of the pitch binder.

Sulfur cannot be used with all carbonaceous binders, but only with those having a softening point less than 300 C., such binders hereafter being denominated sulfur-reactive binders. This temperature limits allows the binder to be melted and distributed in the carbon aggregate before the sulfur causes excessive dehydrogenation of the binder. For this reason, binding materials such as coal and green coke which possess high softening temperatures cannot be used with sulfur for the purpose of the present invention. Suitable binder materials are coal tar pitch, coal depolymerization pitch and wood pitch having the indicated softening point.

Additionally it has been observed in the practice of the pressure baking process of interest that the number of pitch-bonded mixes which can be run without difficulty depends upon product weight. In the absence of sulfur in the pitch bonded mix, one or two 200 pound charges or sufficient to produce only four or five blocks 7 inches by 7 inches by inches in size give ofi enough condensate'to cover the entire area near the mold. By

'used with sulfur and without sulfur.

contrast when using sulfur and pitch, over 3000, such blocks equivalent to more than 45,000 pounds of mix have'been made without the need to clean the external parts of the press.

A large number of tests of the invention have been made. In such tests conventional mixes have been modified by the addition thereto of sulfur in accordance with the invention, and articles have been produced from the modified mixes. In typical tests, articles were produced from two basically similar mixes, both of which were Each of the mixes was composed of Calcined Ingredients, these being of petroleum coke of different particle sizes, and Binder, the binder being a coal tar pitch having a melting point of 175 C. The composition of the mixes used in these tests is tabulated below:

TABLE I Mix Composition Calcined Binder-Percent Mix No. Ingredients of Calcined Ingredients Percent Percent Pitch Sulfur Coke A 1 Coke B 1 25 15 Nil 25 75 15 3 50 50 15 Nil 50 50 15 3 1 Particle sizes of: Coke A=0.015 inch to 0.03 inch. Coke B=55 percent through 200 mesh; 45 percent on 200 mesh (0.074 mm. openings).

In a series of tests conducted utilizing the mixes set forth in Table I, two different sizes of articles were produced. The first was a circular disc 1% inches in diameter by inch thick. The second type of article produced was a brick measuring 9 inches by 4% inches by 2 /2 inches. When mixes Nos. I and III were used (these mixes containing no sulfur), heavy, dark condensable fumes were produced, When mixes Nos. II and IV (that is, those containing sulfur) were used, under the same conditions, only light fumes which produced no condensate were formed. The apparent density of articles produced from the sulfur-containing mixes was only slightly greater than the apparent density of articles produced from the conventional mixes, indicating that most of the sulfur escaped during processing by combining the volatile constituents of the pitch binder. For example, the apparent density of a brick produced from mix No. I was 1.722 grams per cc., whereas a similar brick produced under similar conditions from mix No. II was 1.738 grams per cc. The longitudinal flexural strength of the brick produced from mix No. I was 3570 pounds per square inch, whereas that produced from Mix No. II was 3850 pounds per square inch.

What is claimed is:

1. In a process for making a formed carbon article from a mix consisting primarily of comminuted carbonaceous particles and fusible carbonaceous binder, said binder tending to evolve substances which condense on the apparatus used in said process, placing said mix in a mold, subjecting said mix within said mold to a high mechanical pressure to compress the same while passing an electrical current through said mix to heat the same to carbonization, the improvement which comprises providing in said mix in an amount ranging from 3 percent to 20 percent by weight of said binder material, said sulfur reacting with the substances evolved from said binder to form non-condensing materials whereby unwanted accumulation of condensible substances on said mix within said mold to a high mechanical pressure to apparatus is avoided. compress the same; while rapidly heating the compressed 2. A process for making a formed carbon article commixture to carbonization.

prising forming a mix comprising comminuted carbonaceous particles, sulfur, said sulfur being present in an 5 References Cited in the file of this patent amount ran ing from 3 percent to 20 percent by weight of binder, aild comminuted particles of a sulfur-reactive UNITED STATES PATENTS pitch binder having a melting point not in excess of 300 1,017,483 Van Brunt Feb. 13, 1912 C.; enclosing said mix within the mold; subjecting said 1,390,823 Sieurin Sept. 13, 1921 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No. 2,965 931 December 27, 1960 -Lorne B. Alden et a1.

It is hereby certified that error appears in the above numbered patent re uiring correction and that the saidLetters Patent should read'as corrected below.

Column 2 line 69, after "mix". insert sulfur Signed and sealed this 6th day of June 1961.

- (SEAL) Attest;

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

1. IN A PROCESS FOR MAKING A FORMED CARBON ARTICLE FROM A MIX CONSISTING PRIMARILY OF COMMINUTED CARBONACEOUS PARTICLES AND FUSIBLE CARBONACEOUS BINDER, SAID BINDER TENDING TO EVOLVE SUBSTANCES WHICH CONDENSE ON THE APPARATUS USED IN SAID PROCESS, PLACING SAID MIX IN A MOLD, SUBJECTING SAID MIX WITHIN SAID MOL TO A HIGH MECHANICAL PRESSURE TO COMPRESS THE SAME WHILE PASSING AN ELECTRICAL CURRENT THROUGH SAID MIX TO HEAT THE SAME TO CARBONIZATION, THE IMPROVEMENT WHICH COMPRISES PROVIDING IN SAID MIX IN AN AMOUNT RANGING FROM 3 PERCENT TO 20 PERCENT BY WEIGHT OF SAID BINDER MATERIAL, SAID SULFUR REACTING WITH THE SUBSTANCES EVOLVED FROM SAID BINDER TO FORM NON-CONDENSING MATERIALS WHEREBY UNWANTED ACCUMULATION OF CONDENSIBLE SUBSTANCES ON SAID APPARATUS IS AVOIDED. 